- Introduce log levels trace1/.../trace8

- Add macro wrappers for ap_log_*error. On C99, this will save argument
  preparation and function call overhead when a message is not logged
  because of the configured loglevel.
- Introduce per-module loglevel configuration.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@951893 13f79535-47bb-0310-9956-ffa450edef68